Is Vitamin B12 Safe with Metformin?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Long-term metformin use can lower B12 over years (often >4 years). Guidelines recommend periodic B12 monitoring — not avoidance of either agent.
Why this interaction occurs
Metformin may reduce calcium-dependent ileal absorption of vitamin B12. Effect is gradual; periodic monitoring is sufficient.
Evidence
Evidence level: strong.
Data source
NIH ODS / ADA Standards of Care; MedlinePlus metformin
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 432,898 reports mentioning Metformin. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the Metformin + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Vitamin B12 interactions → · All Metformin interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.